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Old 05-08-2017, 03:10 PM   #31
Anthony
 
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by weby View Post
Yes, but there are quite likely plausible designs that can stop 5.56 AP(avg pen 35) with less deformation than 7.62 ball(avg pen 24) as the strike energy of the 5.56 is so much smaller.
The thing is, the deformation from 7.62 is about adequate to do 1 point of damage, so 'less deformation' means 'no damage'.
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Old 05-08-2017, 04:02 PM   #32
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Anthony View Post
The thing is, the deformation from 7.62 is about adequate to do 1 point of damage, so 'less deformation' means 'no damage'.
But if one uses your proposed model where just failing to penetrate causes 1 point. And then you have a DR 35 armor like quite many armors in GURPS. Using armor as dice so the unrealistic damage fluctations do not affect it will just stop AP 5.56. But the same armor will stop the 7.62 Ball with 11 points to spare so nowhere near the maximum and yet the 7.62 has a lot more energy so it might well cause more deformation despite being 11 points short of penetration.

Basically both get stopped by the armor, but in the 5.56x45 from short range from rifle length barrel the armor has to spread about 1750J but with a 7.62x51 from close range you have to spread about 2200J.
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Old 05-08-2017, 04:12 PM   #33
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by weby View Post
Basically both get stopped by the armor, but in the 5.56x45 from short range from rifle length barrel the armor has to spread about 1750J but with a 7.62x51 from close range you have to spread about 2200J.
More like 3200J, but what do you mean by 'spread'? Very little of the kinetic energy gets transferred into movement of the plate -- most of it gets expended on heat, sound, possible ricochet and fragments, and deformation or cracking of projectile and plate, and the job of the armor is to make sure most of that occurs on the outside, not the inside.
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Old 05-08-2017, 04:34 PM   #34
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Anthony View Post
More like 3200J, but what do you mean by 'spread'? Very little of the kinetic energy gets transferred into movement of the plate -- most of it gets expended on heat, sound, possible ricochet and fragments, and deformation or cracking of projectile and plate, and the job of the armor is to make sure most of that occurs on the outside, not the inside.
What I mean with spread is that all that energy has to go somewhere, as example by the methods given by you. Different materials do different things when that energy comes in but it has to deal with it somehow. It is not simply the penetration through that has to be stopped but also the amount of internal bulging has to be limited. A modern style hard body armor is a compromise of the different requirements. Some types are better at single shot protection but the best materials/weight for such tend to not be anything close to the optimal for resisting multiple shots.

So as example of the thing I am talking about: You have a armor optimized to stop 5.56N AP round, but just barely to keep it light accepting that some deformation is OK as long at it is not at life threatening levels. So the armor stops the bullet and deforms X amount. Then the armor is hit by a 7.62N Ball round. In case the face of the armor is not able to bounce the round by deflection type mechanisms there should likely be some deformation.

In the proposed model such a vest(DR 35 in GURPS terms) would thus cause 1 HP crush though with 5.56 but the 7.62 would not even come close to doing it. I find this unrealistic for plates where part of the protection mechanism is the deformation.
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Old 05-09-2017, 03:53 AM   #35
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by DeathDaisy View Post
Aha, I'll check it out, sounds like a reasonable rule.
I find it works well (but IMO needs the bleeding rules as well)


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Originally Posted by DeathDaisy View Post
Fair enough, I'm far, far from an expert and just went with gameablity, so I'll concede :) Might still try it in my own games tho, see how it works out, maybe cap the damage at even less, just a few points or so.
No worries, neither am I, give it a go and see how it works!

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Originally Posted by Varyon View Post
Bullets usually don't have that kind of momentum. A bullet fired from a tank's main gun, or even "just" a mounted anti-materiel rifle, could very well have such. Like I said, it's not entirely unrealistic, just extremely unlikely, as the sort of impact pressures that would have to be involved will usually punch through the armor.



Look at the kind of damage you need for that knockback - my example called for a DR 60/5 armor before the effect came into play. You don't get this kind of performance with weapons that can be hip-fired. As for the action-reaction effect, I don't think there's a single weapon where MinST is low enough for an average hit* to knock the wielder back, and considering the shooter is going to be better braced for impact than the target, things should work out alright here. Yes, this does mean an M14 will, on an average-but-nonpenetrating hit (meaning he'd need to be wearing armor that would put Ned Kelly's to shame), knock an ST 10 character back one yard. Part of that is GURPS' unrealistic (but easy to use) knockback rules, of course, but for the modest cinematics GURPS defaults to, it doesn't seem like a bad rule. The lesser reduction for pi++ means you only need around 4d+2 to manage that knockback, which can be a bit more problematic, but not game-breakingly so.

*Higher than average damage with a firearm doesn't mean a more powerful bullet, it means hitting a higher-value target, impacting at a better angle, or similar.

Ah OK right, sorry I thought you we're referring to the proposed house rule, yeah, tanks guns etc lots of momentum! (at the personal level)

EDIT: sorry just looking again at the second second section of this, I'm no sure what you mean when linking MinST to Knock back? And I'm not sure a 10g bullet travelling 830m/s will knock back a human sized target (in lots of armour) a yard if it collides but doesn't penetrate. But then knock back in GURPS is a lot of different things.



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Originally Posted by Anthony View Post
It's actually just a conversion of RL to RL. Basically, the NIJ standards for armor specify a list of attacks that must fail to penetrate, and also specify a maximum amount of backspace deformation by listed attacks. The maximum appears to be 44mm, which is actually quite a bit; enough that a point of non-penetrating damage seems reasonable (this is actually a sort of reasonable general rule -- since the backface standards are consistent, just assume any attack that barely fails to penetrate does 1 point of blunt trauma, and ignore the existing rules for nonrigid armor).

However, level IV armor is rated to stop 7.62mm AP, and while there are no specific standards for resistance to weaker threats other than they also have to not get through, there's not really a plausible design for plates that suffers the same deformation against 5.56mm as it would against 7.62.
I think I'd hesitate before I'd equate 44mm of back deformation to 1pt of damage, simply because I don't think there's such a RL to GURPS conversion rate.

What's 1pt of damage or 2 points etc is subject to an awful lot of variable beyond just how far back did the plate push/bulge

However that said as per my post 18 I don't actually think the best way to look at this is have 1 or 2 (or whatever) damage applied uniformly, as blunt trauma usually is. But rather to call it Cr and allow it the varied effects on location as per MA injury rules.

Last edited by Tomsdad; 05-09-2017 at 06:20 AM.
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Old 05-09-2017, 04:14 AM   #36
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by weby View Post
What I mean with spread is that all that energy has to go somewhere, as example by the methods given by you. Different materials do different things when that energy comes in but it has to deal with it somehow. It is not simply the penetration through that has to be stopped but also the amount of internal bulging has to be limited. A modern style hard body armor is a compromise of the different requirements. Some types are better at single shot protection but the best materials/weight for such tend to not be anything close to the optimal for resisting multiple shots.

So as example of the thing I am talking about: You have a armor optimized to stop 5.56N AP round, but just barely to keep it light accepting that some deformation is OK as long at it is not at life threatening levels. So the armor stops the bullet and deforms X amount. Then the armor is hit by a 7.62N Ball round. In case the face of the armor is not able to bounce the round by deflection type mechanisms there should likely be some deformation.

In the proposed model such a vest(DR 35 in GURPS terms) would thus cause 1 HP crush though with 5.56 but the 7.62 would not even come close to doing it. I find this unrealistic for plates where part of the protection mechanism is the deformation.

Remember Armour Divisors apply to the DR not the damage roll.

Divide the target’s DR by
the number in parentheses before subtracting
it from basic damage;
Campaigns pgg378

So when it comes to comparing damage for blunt trauma it's not:

5.56 AP average penetration 35 vs. 7.62 average penetration 24

but:

5.56 AP average damage 17 vs. 7.62 average damage 24

So it still fine for the 7.62mm to deform the plate more, even if due to it's AP effect the 5.56 is better at penetrating it

Last edited by Tomsdad; 05-09-2017 at 04:40 AM.
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Old 05-09-2017, 04:43 AM   #37
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Tomsdad View Post
So it still fine for the 7.62mm to deform the plate more, even if due to it's AP effect the 5.56 is better at penetrating it
That is exactly my point.
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Old 05-09-2017, 04:51 AM   #38
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by weby View Post
That is exactly my point.
And that's what you get, so long as you compare the damage rolls and use the the damage rolls to assess deformation and blunt trauma etc, and not the penetration which is drastically improved for the 5.56 because it has the AD(2)

i.e 17 vs 24, not 35 vs 24

EDIT: Sorry I should add weather or not that will correspond to more blunt Trauma is going to depend on the threshold system you use.

Anthony's system was half of the DR counts as flexible and the other half rigid so with DR35* neither 5.56AP or 7.62 would give you blunt trauma under it (but only because the threshold is 10, the 7.62 is closer to doing so than the 5.56). If you just count it all as flexible then you'd get 1 point from the 5.56AP, and 2 from the 7.62.

But really that's just a matter of tinkering around the edges to allow a 5.56 to not give any and the 7.62 to give some.

For instance treat the plate as flexible, and calculate blunt trauma as you normally would, but subtract 1 from the result.


*but then a DR35 plate is a pretty serious plate

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Old 05-09-2017, 11:33 AM   #39
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

I certainly agree strong enough non penetrating Thrusting attacks should count if strong enough swings do*

(the difference in swinging and thrusting forces for generating can be shown by the difference between basic Thr and Sw damage)


Somethings also need to be adjusted on an individual basis (a v.fine cutting sword that gets +2 damage for being extra sharp etc, shouldn't be better at knocking people back if it fail to get past DR)



*Equally I see no reason why swung imp attacks risk getting stuck, but thrust imp ones don't. I'd prefer to make it function of Imp damage in some way, as I also don't see why a 2 point Swung Imp injury is as prone to get stuck as a 12 point one (just as I don't see what 2 point swung Imp wound risks getting stuck, but a 12 point thrust imp wound doesn't)

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Old 05-09-2017, 12:23 PM   #40
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by weby View Post
But if one uses your proposed model where just failing to penetrate causes 1 point.
An easy solution here is to base the "just failed to penetrate" off of basic damage, without armor divisors in play. An armor piercing round that fails to penetrate does nothing, even if it were only a point shy, while a normal round that just fails does 1 point of injury. Now you'll never have the issue of a lighter armor piercing round causing more deformation than a heavier round.

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Originally Posted by Tomsdad View Post
EDIT: sorry just looking again at the second second section of this, I'm no sure what you mean when linking MinST to Knock back? And I'm not sure a 10g bullet travelling 830m/s will knock back a human sized target (in lots of armour) a yard if it collides but doesn't penetrate. But then knock back in GURPS is a lot of different things.
For the first, that was in reference to the action/reaction bit - that is, if a bullet can push a person back a yard then firing it should push that same person back a yard as well. As Knockback Threshold is based on HP, and HP is based on ST, it makes some sense to assume the typical wielder of a weapon will have HP equal to or exceeding MinST, which will give us the amount of Knockback the character would suffer from firing the weapon without properly bracing himself for the recoil (there are no rules for adjusting Knockback when there is bracing involved, but it would make sense to reduce Knockback in such cases). To my knowledge, there aren't any firearms that the Knockback calculated using my proposed houserule would be enough to knock the firer back a yard or more (there's a musket in HT that comes dangerously close - 4d+1 pi++ and ST10 - but none that actually reach this point). Bows and crossbows might be a different story, but that's an issue with the unrealistic ST-based damage table.

For the latter, I calculated the impact damage using the Collisions rules from Tbone's GULLIVER rules, which are designed to be more realistic than the default GURPS rules. I only calculated it for three projectiles, however - the 5.56x45mm, 7.62x39mm, and .50 BMG - and extrapolated from there, so the actual crushing damage of other bullets may not be as suggested in my houserule. Unrealistic Knockback results may be more an issue with the Knockback rules than with the crushing component of bullets.

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Originally Posted by Hellboy View Post
B378's Knockback rules could benefit from some expansion.
Post #4 of my previously linked thread does a lot of this, by essentially giving every attack a crushing component (which would have Knockback associated). Having attacks that are partially blocked only have Knockback from the portion of the damage that is blocked is a logical addition.

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Originally Posted by Tomsdad View Post
Somethings also need to be adjusted on an individual basis (a v.fine cutting sword that gets +2 damage for being extra sharp etc, shouldn't be better at knocking people back if it fail to get past DR)
Again, the previously-linked thread has this effect built-in.

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Originally Posted by Tomsdad View Post
*Equally I see no reason why swung imp attacks risk getting stuck, but thrust imp ones don't. I'd prefer to make it function of Imp damage in some way, as I also don't see why a 2 point Swung Imp injury is as prone to get stuck as a 12 point one (just as I don't see what 2 point swung Imp wound risks getting stuck, but a 12 point thrust imp wound doesn't)
With a swinging attack you have a bit of build-up of momentum during the swing, which you don't have for pulling it back out, so it's harder to pull back out than it was to initially put in. This isn't the case with thrusting. That's the idea, anyway - in reality it's certainly possible to get a thrust impaling weapon stuck so that it takes a moment to pull out, but (outside of barbed weapons) this is treated as below GURPS resolution.
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